Step 1: Preheat the Oven
Preheat your oven to 350°F (175°C).
Grease and flour two 9-inch round cake pans, or line them with parchment paper.

Step 2: Combine the Dry Ingredients
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Step 3: Add Wet Ingredients
Add the eggs, milk, vegetable oil, and vanilla extract to the dry ingredients.
Beat with an electric mixer on medium speed for 2-3 minutes until the batter is smooth and well combined.

Step 4: Add the Boiling Water and Sour Cream
Stir in the sour cream (or buttermilk) for extra moisture.
Slowly pour in the boiling water, mixing constantly. The batter will be thin, but this is normal and will result in a moist cake.

Step 5: Bake the Cake
Divide the batter evenly between the prepared cake pans.
Bake for 30-35 minutes, or until a toothpick inserted into the center of the cakes comes out clean.

Step 6: Cool the Cakes
Allow the cakes to cool in the pans for about 10 minutes.
Then, remove the cakes from the pans and transfer them to a wire rack to cool completely.

Step 7: Make the Frosting (Optional)
In a large bowl, beat the softened butter with an electric mixer until light and fluffy (about 3 minutes).
Gradually add the powdered sugar and cocoa powder, alternating with the milk, and beat until the frosting is smooth and creamy.
Stir in the vanilla extract and a pinch of salt.

Step 8: Assemble and Frost the Cake
Once the cakes are completely cool, spread frosting on top of one cake layer.
Top with the second layer and frost the top and sides of the cake with the remaining frosting.

Step 9: Serve
Slice and enjoy! For an extra touch, sprinkle some chocolate shavings or a dusting of cocoa powder on top of the frosted cake.